1. Field of the Invention
The invention relates generally to a method of manufacturing a capacitor in a semiconductor device, and more particularly to, a method of manufacturing a capacitor in a semiconductor device in which metal having a good oxide-resistant is used to form an underlying electrode, thus lowering the effective thickness of the Ta2O5 to increase the capacitance of a capacitor in a capacitor using Ta2O5 as a dielectric film.
2. Description of the Prior Art
Generally, as semiconductor devices become higher integrated and miniaturized, there is a trend that the area occupied by capacitors also become small. Even though the area of the capacitor becomes smaller, the capacitance of the capacitor required to drive the device must be secured. In order to secure the capacitance, it is required that the underlying electrode be formed in a three dimensional structure for increasing the effective surface area. However, this method has a complicated process. Thus, it is impossible that it is applied to a higher integrated semiconductor device having more than 256M DRAM. Another method of securing the capacitance is a method of manufacturing a capacitor by using a dielectric having a high dielectric constant.
Recently, a research by which Ta2O5 having the characteristic of a high insulation-breakage voltage while having the dielectric constant of 20-25 is used as capacitor materials for Giga DRAM, has been actively progressed. Generally, the Ta2O5 capacitor uses poly-silicon as an underlying electrode and TiN as an upper electrode. However, the Ta2O5 capacitor is thick in about 30-35 xc3x85 in the thickness of the effective oxide film Tox. As it also uses TiN as an upper electrode, if a high temperature process at more than 750xc2x0 C. is performed after TiN is deposited, there is a problem that the thickness of the effective oxide film is further increased. In this type of Ta2O5 capacitor having a MIS structure, in order to compensate for reduction of capacitance due to increase of the thickness of the effective oxide film, the underlying electrode is usually made of a cylindrical structure to increase the effective surface area. However, in order to make a high cylindrical structure more than 1.0 xcexcm, there is limits to increase the effective surface area due to difficulty in the process.
Further, when depositing Ta2O5 or performing a thermal treatment process for crystallization under a high oxygen atmosphere, an underlying electrode and a diffusion prevention film in the Ta2O5 capacitor are likely to be oxidized. Thus, there is a problem that the leak current is increased to degrade the electrical characteristic of the capacitor.
It is therefore an object of the present invention to provide a method of manufacturing a capacitor in a semiconductor device, which can not only lower the thickness of the effective oxide film of Ta2O5 but also prevent increase of the leak current due to oxidization of an underlying electrode and an diffusion prevention film in a capacitor using Ta2O5 as a dielectric film.
In order to accomplish the object, a method of manufacturing a capacitor in a semiconductor device is characterized in that it comprises the steps of providing a semiconductor substrate in which a contact plug having a recess is formed; forming a contact film and a diffusion prevention film within the recess of the contact plug; forming a sacrifice oxide film in which a hole pattern through the diffusion prevention film is exposed formed; forming an oxide-resistant conductive layer on the entire structure including the sacrifice oxide film in which the hole pattern is formed; remaining the oxide-resistant conductive layer in the hole pattern and removing the sacrifice oxide film, thereby forming an underlying electrode of a cylindrical structure; forming a Ta2O5 dielectric film on the underlying electrode; and forming an upper electrode on the dielectric film.